First, please refresh the Google Docs page and start VideoSnack again.
If the issue persists there are a few reasons this might happen:
You are using a different email address than the one you purchased your license with. The login email address must be the same with the email address you use with Google Docs, that is your license. If you purchased your license with a different email please contact us.
You used an email from another email provider than Google. Our licenses can be used only with Gmail or Google Workspace accounts/domains. If you did that please contact us.
You are logged in with a multiple emails, please log out of all accounts and log in only with the email account that your licensed is assigned.